1. Field of the Invention
The present invention relates to the suspension of the rotor of the low pressure turbine of a twin hub turbo-engine.
2. Summary of the Prior Art
French Patent No. 1 462 062 discloses a gas turbine engine with a rear mounted fan in which the fan comprises a rotor having a single stage of blades connected to short front and rear shafts which are respectively supported by bearings. The bearings themselves are carried on the stationary structure of the turbofan through the intermediary of struts or fins disposed upstream and downstream of the turbofan.
French Patent No. 1 527 370 discloses a turbojet engine with a front mounted fan in which the low pressure turbine rotor comprises several stages of blades fixed to a drum carried at its two ends by conical elements journalled in roller bearings carried respectively on radial spacers by means of conical support members placed upstream and downstream of the low pressure turbine, the spacers being attached to the casing of the engine.
The suspension systems for the rotors of the low pressure turbines disclosed in these two documents comprise elements for the suspension of said rotor disposed upstream and downstream of the low pressure turbine, which involves problems and expense in assembling and dismantling the engine.
To facilitate the assembly and dismantling of the engine, it is known that the radial spacers placed upstream of the low pressure turbine may be dispensed with by using an inter-shaft bearing between the high pressure hub and the shaft of the low pressure turbine.
However, supporting the low pressure rotor solely from the rear of the low pressure turbine confers on the low pressure shaft a major degree of flexibility which can generate excessive vibrations in this turbine, and there is a danger of vibratory energy being transmitted from one hub to the other by virtue of the fact that the high pressure hub is carried on the low pressure shaft.
It is also known that the radial spacers placed downstream of the low pressure turbine may be dispensed with by having the low pressure turbine supported only at the front by means of an inter-turbine casing sited between the low pressure and high pressure turbines. This type of mounting can also engender undesirable vibrations, particularly if the low pressure turbine comprises a large number of stages.